Electrode manufacture



Jan. 15, 1946. T4, RADCUFFE 2,392,879

ELECTRODE MANUFACTURE Filed June 29, 1942 lnvencor': Thomas J. Radcti++e,

His A't'torneg.

Patented Jan. 15, 1946 ELECTRODE MANUFACTURE Thomas J. Radcliffe, Believille, N. J.,- assignor to General Electric New York Company, a corporation of Application June 29, 1942, Serial No. 449,027

1 Claim.

'l,965,586, issued July 10, 1934. Such electrodes are known as "cold type' electrodes as distinguished from hot or incandescible electrodes which are'usual ly made of wire or ribbon. This patent also discloses the use of aluminum or aluminum oxide, among other materials, for excluding the glow discharge from the inner surface of the electrodes and confining said discharge to the outer hemispherical surface presented thereby. Heretofore the aluminum or aluminum oxide, hereinafter called anti-glow material, has been painted on the inner surface of the electrodes by hand with a small brush. This is a slow, expensive method not suitable for mass production, and one in which complete and uniform coverage of the desired surface is not always obtained.

and Fig. 3 is a perspective view of an electrode punched out of the strip.

Referring to Fig. 1 of the drawing, the apparatus comprises a supply reel l0 which furnishes a strip ll of uncoated metal. The strip II is continuously unwound and drawn in the rirection of the arrow through the guide block I! by the motor driven feed rollers H! which may have a soft rubber surface. A pair. of centering guides it direct the strip ll between the pressure roller l5 which may be of soft rubber and the applicator roller l6 which may have a steel surface. The roller i5 presses the strip Ii down on the roller I 6 which runs in a bath of aluminum paint. The face of the roller i6 is narrower than the width of the strip ll so that an even coating of aluminum paint is applied along the center portion of one side of said strip ll An object of my invention is to facilitate the manufacture of such lamps by providing an improved process of manufacturing such electrodes or cathodes including the method of and a means for applying the anti-glow material to the desired area of the electrodes. Further objects and advantages of my invention will appear from the following detailed description thereof. A feature of my invention is the application of anti-glow material to suitable portions of the metal body out of which a plurality of elec- \diagrammatically in Fig.1; Fig. 2 is a top plan view of a portion of metal strip coated with antiglow material by'the apparatus shown in Fig. 1:

as it is drawn in the direction of the arrow.

The uncoated side of the strip I I is then passed upward over the stationary electrical contacts ll, i8 and I9 mounted on the electrically insulating support '20. Said contacts l1, l8 and I9 are connected to a source of electrical energy capable of passing suflicient energy through the ever-changing portion of the strip ll bridging said contacts to raise it to the baking temperature of the paint. Two sheaves 2| and 22 mounted on the support 20 guide the coated strip ll downward from the contact I! to the collecting reel 23 which is driven by the motor M acting through the friction clutch 25. The portion of strip ii passing over the contacts ll, l8 and i9 and the sheaves 2i and 22 is of looplike shape as shown in the drawing.

The contacts If and I9 are each connected to a terminal of the secondary of a step-down transformer 25 and the contact I8 is connected to the mid-point thereof. The primary of said transformer 26 is connected across the terminals of an alternating current source. I have demonstrated that a current of about 50 amperes through the ever-changing painted portion of the strip H bridging the contacts is effective for heating said portion sufliciently to produce an adherent, uniform, baked-on coating of antiglow material on a nickel strip having a width of approximately inch and a thickness of approximately .010 inch when the speed of the strip II is such that a given point thereon is heated for approximately 5 seconds. A transformer capable of changing a 220 volt current supply While the center contact II and its connection to the transformer secondary may be omitted, I have found that it minimizes sparking at the contacts I1 and II and is therefore desirable. Further, the contact ll avoids overheating parts and underheating other parts or the portion of the strip H bridging the contacts l1 and.

25 tends to drive the collecting reel 23 at a higher rate of motion and to pull the strip ll through the apparatus at a higher speed than the feed rollers 18 will allow. Sufficient tension is thus exerted on the loop-like portion of the strip H to hold the latter firmly against the contacts I1, is and It to avoid excessive sparking between the strip and said contacts. The strip II is passed between the contacts I1 and I9 at a rate such that the paint is thoroughly baked thereon without impairing the ductility of the strip II for the subsequent shaping of the electrodes. This rate may be determined by trial runs of the apparatus. Undue heating of the contacts, particularly contact ill, by the hot portion of the strip ll passing over its surface may be prevented by providing suflicient heat dissipating capacity. If the heat dissipating area of the contact itself is not sufilcient for this purpose then heat radiating fins or liquid cooling means may be used.

I have demonstrated that the paint sold by the Sahlin Chemical and Color Company of Camden. N. J under the designation of No. 2056 Aluminum is eminently satisfactory for use in the above process. The composition of this paint is approximately 35 per cent aluminum. 52 per cent mineral spirit, 11 per cent China-wood oil and 2 per cent acid resin. The paint may he applied to the center portion of the strip l l by hand and dried in air atroom temperature or at an elevated temperature, such as in an oven.

The coating on the strip ll isindicated by dots to leave a coating of aluminum on the innersurface thereof. The firing also cleans the surface of the electrodes. I prefer to use an atmosphere of moist hydrogen to avoid the formation of complex hydrocarbons in the firing operation.

What I claim as new and desire to secure by Letters Patent of the United States is:

The method of manufacturing concave cold type electrodes having a metallic coating on their inner surfaces which comprises coating one side of an elongated metal strip with a suspension of powdered anti-glow metallic material in a volatilizable binder, baking the coating by passing the uncoated side of the strip over spaced electrical contacts connected to a source of current to heat the portion of the strip between said contacts to a temperature which is sufficiently high to bake the coating but too low to impair the ductility of the metal strip, forming and punching a multiplicity of concave electrodes from the strip with the coated side forming the inner surface of the electrode, and then firing the electrodes at a temperature sufllciently high to drive oi! the binder and leave an adherent coating of the metallic material on the inner surfaces oi the electrodes.

THOMAS J. RADCLIFFE. 

